Live stream view fixes and identifiers

A batch of changes hardened analytics for live streams.

• Fixed a 404 page-not-found error that surfaced when opening individual live-stream views.
• Added fp_live_stream_id, media_id, fp_playback_id and view_has_ad as allowed filter and breakdown parameters on metrics, views and errors APIs.
• The playbackId is now extracted from the vdsour URL during Flink processing, so it is reliably present even when the player didn’t report it explicitly.
• The Device Distribution query was rewritten to fix a “view not counted” bug for some live-stream sessions.